COS 219-5 - Biological control for an American waterlily in South Africa: comparing potential agents in native and invaded ranges.

Abstract: Classical biological control makes use of plant-insect interactions to manage alien invasive plants, but this depends on thorough surveys and host specificity testing, which can be inhibited by complicated genetic structure in the target plant and difficulties in obtaining and rearing insects from other countries. For Nymphaea mexicana, a waterlily that is native to Florida but invasive in South Africa, there is no exception. Research into biological control for this species in South Africa was started in 2016, and although much progress has been made, the hunt for a suitable biological control agent is still underway. Surveys in the native range (USA) and invaded range (South Africa) were carried out over the last five years, revealing American insects that have potential for use as biological control agents, as well as a South African weevil that has expanded its host range to include N. mexicana. This presents an opportunity to compare potential agents in different regions of origin in terms of their host specificity and damage. Hence, this study compares results from host specificity experiments for the South African weevil and American insects carried out in greenhouse and quarantine settings and relates this to their potential for use in managing N. mexicana in South Africa. The results enable us to better focus efforts for management through understanding the factors that govern N. mexicana invasions in South Africa, and also emphasize the importance of international collaboration and of following the steps recommended to develop biological control.